In a bowl cream together sugar, vanilla, eggs and egg whites. Add milk and oil and cream until smooth.

Mix together flour, baking powder and salt. Slowly combine both mixtures. The batter should be liquid in consistence. Divide batter into two and add the cacao powder to one of them.

Preheat oven to 180°C. Grease a baking pan with butter. Now you have to work carefully. Pour 3 tablespoons of the light batter in the middle of the pan. Turn the baking pan 90° degrees and pour 3 tablepoons of the chocolate batter in the middle of the light batter, turn it again 90° degrees. Now take the light batter again and pour again 3 tablepoons in the middle of the chocolate batter, turn again. Continue like this with the rest of the batter.

Bake the cake for about 35-40 minutes until a toothpick comes out clean. Remove from the pan and let it cool completely. Serve with confectioner’s sugar. This cake can be frozen.